In recent years, golf courses and baseball stadiums with lighting systems have been opened. This enables night play. In the case where an ordinary ball is used for night play, the ball can be found if the ball is in a lighted area; however, the ball cannot be readily found or is lost if the ball is in an unlighted area.
A light-emitting golf ball disclosed in Japanese Unexamined Patent Application Publication No. 62-2974 can be used for night play and is similar to one according to the present invention in that the light-emitting golf ball has a self light-emitting function. FIG. 1 of the application illustrates that the light-emitting golf ball has a structure in which a chemical light-emitting body is disposed in a cavity having an inverted triangular shape in cross section and a transparent cover covers the light-emitting body and a core disposed under the light-emitting body. The light-emitting golf ball has a disadvantage in that the illuminant cannot be replaced with another one. Since the light-emitting body is placed perpendicularly to the central axis of the core, that is, the light-emitting body is laid on the core, the length and/or diameter of the light-emitting body is limited. As disclosed in an example, the light-emitting body has a length of 20 mm, an inner diameter of 2 mm, and an outer diameter of 3 mm, that is, the light-emitting body has an extremely small inner volume and therefore can contain only a small amount of a luminescent liquid. Hence, the light-emitting body has disadvantages in that its brightness is low and its light-emitting time is short. In a step of placing the light-emitting body on the core and then forming the transparent cover, a glass vessel disposed in the light-emitting body is broken by the pressure caused by the formation of the transparent cover. This leads to product failure.